Six solar dishes produced by Bruce Osborn’s company, Phoenix, AZ–based Stirling Energy Systems, now stand—each nearly four stories tall—at Albuquerque, NM–based Sandia National Laboratories. The dishes, which together produce about 150 kW of AC power, are serving as a model power plant, a model that Osborn hopes his company will reproduce in far greater numbers during the next five to 10 years.

“This is a big stepping stone toward the large-scale production of commercial solar energy,” Osborn says. “Having this solar plant up and running is a big milestone, one that we’ve been working on for a year-and-a-half. I see a time when there are large, commercial solar plants generating hundreds of megawatts. That’s where we one day see the industry.”

Osborn, who is chief executive officer at Stirling Energy, one of the few major players in the commercial solar industry, is not the only one watching carefully how the model solar plant operates. The plant’s immediate function is to provide energy for the approximately 8,000 employees at Sandia, who will use the plant’s power to light their buildings and pump their air conditioners. But the dishes, which were completely installed in May 2005 at Sandia’s National Solar Thermal Test Facility (NSTTF), have a more important long-term goal: to provide a boost to the commercial production of solar energy in this country.

Much of the solar energy that the US currently consumes comes from photovoltaic systems, says Colin Murchie, director of government affairs with the Solar Energy Industries Association (SEIA), a national trade group supporting the development of the solar industry. Such systems use semiconductor materials that convert sunlight directly to electricity.

The real growth potential for solar energy, though, lies in the widespread commercial production of it, Murchie says. The systems that can accomplish this are known as concentrating solar power (CSP) systems. These use reflective materials to concentrate the sun’s energy into a force powerful enough to operate generators that provide far greater quantities of electricity than photovoltaic systems ever can.

Officials with Stirling dream of one day creating a network of these large generators, locating them in the sun-rich lands of the US Southwest. That’s why Murchie, and other proponents of solar energy, consider the company’s model solar plant at Sandia so important. If the model plant works as it is expected to, and if the engineers at Sandia can fine-tune the plant’s efficiency and make it cheaper to operate and build, the experiment may provide a significant jump-start to the country’s CSP industry.

“The amount of energy actually produced by photovoltaic systems is fairly trivial. The CSP systems, though, have the potential to be far more important,” Murchie says. “These are actual power plants that will be able to generate wholesale electricity. It has the potential to be a significant new arena for the solar energy business. The question on the Stirling engines, really, is manufacturability. If they can figure out a way to manufacture them in a cheap and reasonable way, then it’s off to the races for them.”

The Cost Question
It should be no surprise that expense is the biggest roadblock to the widespread production of CSP systems. It’s also no surprise that Stirling officials are making the cost issue a priority as they study the Sandia model plant.

The production cost for each of the six units at Sandia runs a high $150,000. Stirling Energy officials hope to lower this cost to less than $50,000 for each unit once the systems are in mass production. That figure would be far more competitive with the cost of conventional fuel technologies.

PHOTO: RANDY J. MONTOYA, SANDIA NATIONAL LABS

Osborn knows the price reduction that can result from larger production runs. He started his career in the late 1970s with Ford Motor Co., where he learned just how efficient mass production can be.

“We have been building these units in onesies and twosies,” Osborn says. “If you build, say, a Ford Focus, that is fairly inexpensive to do because of mass production. If you build the onesies, twosies, with a new design, those are very expensive to make. It’s the same with building disc drives. When you go into producing them in mass quantities, they are very inexpensive to build. Doing things in volume is where you are able to get better pricing on raw materials. You can go to automation, too, to get some of the labor cost out.”

Osborn is also placing his hopes on technology, another way he says his firm can reduce the cost of its solar dishes. The experiment at Sandia, he says, will go a long way toward helping Stirling develop technologies to make their equipment both more efficient and less costly.

“We do have a good design already, but there are areas we can improve on in both performance and cost through looking at design and materials,” he says. “We have gone through the entire design of the dish and the power conversion unit at Sandia and we are looking for opportunities for improvement.”

The Sandia model lab has already provided positive results in this area. The company is now testing and seeing good results at the site for its newer dishes, ones that contain better-performing mirrors. The mirrors have a lower content of iron than do Stirling’s older-generation versions, meaning they transmit more energy from the sun than do these older models. The original design for the company’s dishes sported a reflexivity rate of 91%. The new models operating at Sandia, though, have boosted that percentage to 93% or 94%.

This is critical, Osborn says. The new dishes—each comprising 82 individual mirror panels— can now transmit a more focused, narrower beam of solar energy into a power generator. Stirling’s early findings show that this increased energy concentration results in an additional 1 kW of power.

Successes like this, Osborn says, are the first step in the creation of large-scale solar power plants. The experiment at Sandia, in fact, is the largest solar plant Stirling has ever operated. The company does have individual solar dishes running near the campus of the University of Nevada - Las Vegas; in Huntington Beach, CA; and in Johannesburg, South Africa. But none of these single dishes carries with them the same hopes as do the dishes at Sandia.

“This is an exciting time for us,” Osborn says. “We do have it in our business plans that in the next couple of years we’ll put in a 1-MW pilot plant that will have 40 or so Stirling dishes. We’re looking to go on a larger scale soon. For now, though, we’ll continue to evaluate our system’s performance at Sandia. Part of our commercialization efforts involve the need to improve the performance of our system, to reduce the amount of time it takes to manufacture these, and to reduce the costs of these systems. After that, we expect to go into the large-scale commercialization of these systems.”

The Sandia Experiment
Sandia has long supported the production of solar energy. Its National Solar Thermal Test Facility is the country’s leading site for solar energy experiments, so the partnership between Sandia and Stirling made sense.

Stirling’s model plant now provides enough grid-ready electricity to power more than 40 homes, something that Sandia officials agree is an important development. But Sandia officials, like those at Stirling Energy, are focused more on the future production of solar energy that experiments like the model power plant can help bring about.

“This will be the largest array of solar dish–Stirling systems in the world,” said Chuck Andraka, the project’s leader at Sandia, in a written statement. “Ultimately, Stirling Energy Systems envisions 20,000 systems to be placed in one or more solar dish farms and providing electricity to southwest US utility companies.”

Each Stirling Energy unit consists of 82 mirrors formed in the shape of a dish. These mirrors are laminated onto a honeycomb aluminum structure.

Each unit operates automatically, with no assistance needed from any operators. At dawn, the systems start. They then operate throughout the day, moving back and forth according to the clouds and available sunlight. The machines shut themselves down at sunset. Researchers are able to monitor the system through the Internet. The goal is to bring the technology that makes this system work to much larger commercial systems in the future.

The dishes generate electricity by focusing the sun’s rays onto a receiver that transmits heat energy to an engine, a sealed system filled with hydrogen. As the gas heats and cools, its pressure rises and falls. The change in pressure drives the pistons inside the engine, which produces mechanical power. This drives a generator that makes the electricity.

The key to efficiency lies in making sure that all six dishes work together well.

“It’s one thing to have one system that can operate but a whole other thing to have six that must work in unison,” Andraka says.

The Sandia plant is modular in nature. This is important because it can be added onto over a period of time, something that is critical for Stirling Energy’s plans to create large-scale, commercial solar-energy plants. It is far more efficient to grow in this manner than it is to work with a traditional power plant that crews would have to completely re-build before they become operational.

Moving from one model power plant at a testing site to a vast network of commercial solar plants is a major challenge, of course. But Andraka, for one, thinks it is doable.

“It’s a big step to ramp them up the way they want,” Andraka said in a written statement. “But we have such a good relationship with Stirling Energy Systems, and we work together so well, that we should be able to meet this challenge.”

The Future of Solar Power
The Sandia experiment is just one piece of good news for the advocates of solar energy. The federal energy bill signed into law in late July 2005 by President Bush was also a welcome development. The bill provides a number of tax provisions that should help promote the use and development of solar energy.

PHOTO: RANDY J. MONTOYA, SANDIA NATIONAL LABS

Under the new energy bill, homeowners who install solar energy systems will receive a tax credit worth 30% of the system’s cost, capped at $2,000. Businesses that buy solar equipment will also receive a 30% credit.

In a written statement, SEIA president Rhone Resch applauded the provisions.

“These tax credits will bring solar power costs over the tipping point in many areas of the country, and the United States has the best solar resources of any country in the industrialized world,” said Resch.

Earlier this summer, President Bush underscored his support for solar energy—and for increased production of all forms of alternative energy—by touring the NSTTF at Sandia.

“This underscores the message that Washington wants solar power to play a significant role in our nation’s future energy supply,” Resch said.

Murchie says the time is right for the development of solar power. One big reason? Cost.

“For the past 20 years, all the varieties of solar have been getting just a little cheaper every year,” Murchie says. “On average, conventional forms of energy have been getting just a little more expensive every year. A lot of people are sick of the energy market. They’re sick, in particular, of the volatility. The wind and solar fields can act as price hedges to the conventional market.”

Murchie, like most proponents of solar energy, is watching Stirling’s experiment at Sandia closely. He knows that there has been effectively no construction of large-scale CSP systems in the last 15 years.

But he also knows that successful experiments at Sandia can change this.

“The potential here is giant,” Murchie says. “When they come in they are going to be coming in at 50,000-megawatt intervals. There is so much potential here.”

David Slawson, chairman and founder of Stirling Energy Systems, agrees with Murchie. He says he envisions a day when tens of thousands of his company’s dishes work together in a solar dish farm covering less than 11 square miles of US desert. Such a plant, he says, will produce as much electricity as does the Hoover Dam.

And Slawson doesn’t stop there. He also sees a future solar dish farm that covers a patch of land, measuring 100 miles by 100 miles, deep in the southwestern deserts. A farm like this, he says, would generate as much energy as is needed to power the entire US.

Of course, such dreams are far from becoming reality. The truth of the matter is that solar energy, along with wind power and other forms of renewable energy, still makes up an insignificant portion of the energy industry.

This reality, though, doesn’t deter solar’s proponents.

“I think the day when we have large commercial solar plants is approaching quickly,” Osborn says. “There are many factors that are causing the market to change. First and foremost, a lot of states’ renewable portfolio standards, particularly in California, currently stand at 25%. Later in the mid 2010s in California it will increase to 30%-plus. There is a lot of interest and effort around that.”

Then, of course, there is the always reliable anger of residents unhappy with paying ever-increasing fuel costs.

“The public in general is interested in renewables and the environment,” Osborn says. “There are so many concerns over the price of oil and natural gas, that is putting more pressure on the industry to produce more renewables.”

New technology, and improved efficiency, will make the biggest impact, Osborn says. And that’s where projects such as the model power plant at Sandia come in.

“As we and others continue to improve the performance of our systems and reduce their costs, we are getting to the point where very soon there will be a crossing point where renewable energies are cost-effective and competitive with more traditional electric generation sources,” says Osborn. “In the very near future, solar energy—and in particular our technology—will be competitive with peak power generation. We are not going to compete with base load, of course. There is always going to be room for coal, gas, and nuclear power. But we think solar offers some great advantages. We produce peak power during the peak load part of the day.”

DAN RAFTER is a technical writer based in Chesterton, IN.

DE - January/February 2006